You’re running a very old version of Zotero that hasn’t been able to sync since last year. Upgrade to Zotero 5 from the download page to continue syncing.
(You should normally see a message to this effect when trying to sync Zotero 4, but we removed some old code yesterday and accidentally disabled that message. We’ll restore it.)
Upgrade Storage
Same issu with syncing between computer
(You should normally see a message to this effect when trying to sync Zotero 4, but we removed some old code yesterday and accidentally disabled that message. We’ll restore it.)